1. Field of the Invention
The present invention relates to a thin film magnetic head and a method of producing the same. Particularly, the present invention relates to techniques preferably used for a thin film magnetic head having a track width of 1 xcexcm or less, and for a method of producing the same.
2. Description of the Related Art
FIG. 33 is a perspective view showing a magnetic head 150 comprising a conventional combination type thin film magnetic head provided on a slider, and FIG. 34 is a sectional view showing a principal portion of the magnetic head 150 shown in FIG. 33.
The floating magnetic head 150 mainly comprises a slider 151, and a combination type thin film magnetic head 157 provided on the slider 151, as shown in FIG. 33. Reference numeral 155 denotes the leading side on the upstream side of the slider 151 in the movement direction of a magnetic recording medium, and reference numeral 156 denotes the trailing side on the downstream side in the movement direction. In the slider 151, rails 151a and 151b are formed on the medium-facing surface 152 opposed to the magnetic recording medium to form air grooves 151c between the respective rails.
The combination type thin film magnetic head 157 is provided on the end surface 151d on the trailing side 156 of the slider 151.
FIG. 35 is a perspective view showing the principal portion of the combination type thin film magnetic head 157.
The combination type thin film magnetic head 157 comprises a MR magnetic head h1 comprising a magnetoresistive element, and a thin film magnetic head h2 serving as a write head, both of which are laminated on the end surface 151d of the slider 151, as shown in FIG. 34 and 35.
The MR magnetic head h1 comprises a lower shielding layer 163 made of a magnetic alloy and formed on the end surface 151d of the slider 151, a lower gap layer 164 laminated on the lower shielding layer 163, a magnetoresistive element 165 partially exposed from the medium-facing surface 152, an upper gap layer 166 formed to cover the magnetoresistive element 165 and the lower gap layer 164, and an upper shielding layer 167 formed to cover the upper gap layer 166.
The upper shielding layer 167 also serves as a lower core layer of the thin film magnetic head h2.
The MR magnetic head h1 is used as a read head in which a small leakage magnetic field from the magnetic recording medium is applied to the magnetoresistive element 165 to cause a change in resistance of the magnetoresistive element 165 so that a change in voltage based on the change in resistance is read out as a reproduction signal of the magnetic recording medium.
The thin film magnetic head h2 comprises a lower core layer (the upper shielding layer) 167, a gap layer 174 laminated on the lower core layer 167, a coil 176 formed on the back region Y side of the gap layer 174, an upper insulating layer 177 formed to cover the coil 176, and an upper core layer 178 formed to be joined to the gap layer 174 in a pole tip region X and to the lower core layer 167 in the back region Y.
The coil 176 is patterned to have a spiral planar shape. The base end 178b of the upper core layer 178 is magnetically connected to the lower core layer 167 in the central portion of the coil 176.
Furthermore, a protecting layer 179 made of alumina or the like is laminated on the upper core layer 178.
The lower core layer 167, the gap layer 174, and the upper core layer 178 are extended from the back region Y to the pole tip region X of the combination type thin film magnetic head 157, and exposed from the medium-facing surface 152. In the medium-facing surface 152, the upper core layer 178 and the lower core layer 167 are opposed to each other with the gap layer 174 held therebetween to form a magnetic gap.
As shown in FIG. 34, the pole tip region X means the region where the upper core layer 178 and the lower core layer 167 are opposed to each other with only the gap layer 174 held therebetween, and the back region Y means the region excluding the pole tip region X.
The thin film magnetic head h2 is used as a write head in which the supply of a recording current to the coil 176 causes a magnetic flux in the upper core layer 178 and the lower core layer 167 due to the recording current, and the magnetic flux leaks to the outside from the magnetic gap to produce a leakage magnetic field, thereby recording a recording signal by magnetization of the magnetic recording medium due to the leakage magnetic field.
In producing the thin film magnetic head h2, the lower core layer 167, the gap layer 174, and the upper core layer 178 are previously laminated in turn and patterned. The upper core layer 178 is processed by a flame plating method and ion milling, and the exposure width of the upper core layer 178 exposed from the medium-facing surface 152 is defined by the resist width in the flame plating method, and plating and etching processes. The magnetic recording track width is defined by the exposure width of the upper core layer 178 exposed from the medium-facing surface 152.
The magnetic recording track width (the exposure width of the upper core layer 178 exposed from the medium-facing surface on the pole tip side) of the thin film magnetic head h2 is set to a small value to decrease the track width of the magnetic recording medium, thereby increasing the recording density of the magnetic recording medium.
However, the conventional thin film magnetic head h2 has a step formed by the coil layer 176 and the upper insulating layer 177, thereby increasing the thickness of the resist film which constitutes the upper core layer 178. Therefore, even if each of these layers is precisely formed by flame plating, and the pole tip is processed with the present highest processing precision, the limit of resolution in exposure for forming a resist pattern causes difficulties in decreasing the magnetic recording track width to 1 xcexcm or less, thereby causing a problem in that the recording density of the magnetic recording medium cannot be improved.
In some cases, in order to improve the recording density, a magnetic layer made of a material having a high saturation flux density is laminated on each of the lower core layer 167 and the upper core layer 178 to form a two-layer structure, and in order to set a magnetic recording gap depth Gd, a gap layer 174 and a portion 178A of the upper core layer 178 are laminated on the lower core layer 167, and a liftoff resist 81 is formed on the portion 178A of the upper core layer 178, as shown in FIG. 36. Then, an end surface 178a is formed in the portion 178A of the upper core layer 178 by ion milling, as shown in FIG. 37, and an insulating layer 83 is then formed by sputtering or the like, as shown in FIG. 38. FIG. 39 shows a state in which the liftoff resist 81 is removed, and an upper core layer 178B is further formed. FIG. 39 is an enlarged sectional view of portion A shown in FIG. 34, as viewed from the back of the drawing.
In some cases, in the pole tip region X, the back region side end of the portion 178A of the upper core layer 178 which holds the gap layer 174 between the upper core layer 178 and the lower core layer 167, i.e., the end surface 178a which defines the depth of the magnetic gap from the medium-facing surface, gap depth Gd, is not parallel to the medium-facing surface 152, as shown in FIG. 38. In this case, the leakage magnetic field is increased in the vicinity of the end surface 178a, thereby causing the probability of deteriorating the writing ability of the thin film magnetic head, and a position of the end surface 178a where the gap depth Gd is defined is indefinite because the end surface 178a is not parallel to the medium-facing surface 152, as shown in FIG. 38. This causes deterioration or variations in overwrite performance of the write head, and there is thus the demand for precisely setting the gap depth Gd.
With the magnetic gap width set to a small value, in order to form the end surface 178a for defining the gap depth Gd, and form the insulating layer 83, the liftoff resist 81 is used in the production process, in which a notch 81a is formed in the liftoff resist 81 in order to separate a deposited layer 82 deposited on the liftoff resist 81 by sputtering or the like, as shown in FIGS. 36 to 38. Therefore, the liftoff resist 81 is formed to overhang the end surface 178a which defines the gap depth Gd. In this state, the formation position of the end surface 178a which defines the gap depth Gd cannot be discriminated as viewed in plane, thereby causing the problems of deteriorating the setting precision of the gap depth Gd, and deteriorating the overwrite performance of the write head.
In order to separate the liftoff resist 81 and the deposited layer 82, it is also necessary that no deposited layer is deposited in the notch 81a of the liftoff resist 81, as shown in FIG. 38. Therefore, in order to improve the linearity of sputtered particles in formation of the insulating layer 83, long throw sputtering must be used, in which the distance between a substrate serving as the thin film magnetic head h2 and a target is set to be twice a general value. However, this long throw sputtering requires a deposition rate of about 100 angstroms/min, and thus an improvement of low productivity is demanded.
Furthermore, in some cases, in order to prevent a leakage magnetic field from the vicinity of the end surface 178a which defines the gap depth Gd, an apex surface 83a having an inclination with respect to the lower core layer 167 is formed in the insulating layer 83, as shown in FIG. 38. However, with the apex surface 83a having an insufficient angle, an auxiliary layer 84 must be further formed on the insulating layer 83, increasing the number of the work steps, and deteriorating the efficiency of production. There is thus the problem of deteriorating the precision of position setting in the auxiliary layer 84 for the gap depth Gd.
In consideration of the above-mentioned present situation, the present invention is aimed for at least one of the following objects:
(1) To provide a thin film magnetic head having a narrow magnetic recording track width of 1 xcexcm or less corresponding to a track width of 1 xcexcm or less.
(2) To improve the precision of the gap depth of the magnetic recording track from a medium-facing surface in the magnetic head.
(3) To improve the overwrite performance of a write head of a thin film magnetic head.
(4) To provide a method of producing a thin film magnetic head which permits simplification of the production process, and shortening of the production time.
In order to achieve the above objects, the present invention comprises the following construction.
A thin film magnetic head of the present invention comprises an upper core layer and a lower core layer which are extended from a back region to a pole tip region so that the end surfaces thereof are exposed from a medium-facing surface, and which are connected to each other in the back region; a coil provided around the connection portion between the upper and lower core layers; a gap layer provided between the upper and lower core layers in the pole tip region; an insulating layer laminated on the lower core layer; a trench provided in the insulating layer to extend from the medium-facing surface in the pole tip region to the back region so that a lower pole layer and the gap layer are laminated in the trench; a back insulating layer laminated on the back region side of the gap layer; and an upper pole layer laminated on the pole tip region side of the gap layer; wherein the lower and upper pole layers are connected to the lower and upper core layers, respectively, the upper and lower pole layers form the upper and lower pole tips, respectively, the back insulating layer is connected to the upper pole layer and the upper core layer, and the gap depth is determined by the length from the medium-facing surface to the back insulating layer in a portion of the upper pole layer which contacts the gap layer.
In the present invention, the pole tip region side end of the back insulating layer is inserted into between the gap layer and the upper pole layer so that the gap depth can be determined by the pole tip region side end of the back insulating layer.
The back insulating layer of the present invention preferably comprises an apex surface which is inclined so that the thickness increases from the medium-facing surface side to the back region side.
In the present invention, the back insulating layer may be made of a positive photoresist such as a novolak resin.
In the present invention, the technique of providing a part of the coil on the back insulating layer can be used.
In the present invention, the technique of providing the upper pole layer in the trench can be selected.
The exposure width of the gap layer exposed from the medium-facing surface can be set to 1 xcexcm or less.
In the present invention, for example, the upper side of the lower core layer may be polished to a flat surface, the inclination angle of the apex surface of the back insulating layer may be in the range of 10 to 80 degrees with respect to the lower core layer, and the back insulating layer may be continuously extended above the insulating layer.
It is possible to select the technique of laminating a reading magnetic head comprising a MR magnetic head or a GMR magnetic head comprising a magnetoresistive element, and a thin film magnetic head in which the above-described means are selected, to form a combination type thin film magnetic head.
In the thin film magnetic head of the present invention, the lower core layer and the lower pole layer form a lower core, the upper core layer and the upper pole layer form a n upper core, and the lower pole layer, the gap layer and the upper pole layer form a magnetic gap which is interposed between the upper and lower cores.
Since the lower pole layer, the gap layer and the upper pole layer which form the magnetic gap are laminated in the previously formed trench, the magnetic recording track width is determined by the width of the trench.
Therefore, by setting the trench width to a small value, the magnetic recording track width can be decreased to, for example, 1 xcexcm or less on the sub-micron order.
In the present invention, since the gap depth is determined by the length from the medium-facing surface to the back insulating layer in a portion of the upper pole layer which contacts the gap layer, the gap depth of the magnetic gap can be set by the position of the back insulating layer. It is thus possible to prevent variations in the distance from the medium-facing surface to the end of the upper pole layer, and thus prevent variations in the gap depth, improve the overwrite performance of the write head, and decrease variations.
Since the apex surface is formed on the gap depth side of the back insulating layer, a taper portion is formed on the upper pole layer side of the upper core layer. Furthermore, where an inclined portion is formed in the trench, and the upper pole layer is laminated over the inclined portion and the trench main body to be joined to the upper core layer, the taper portion can be formed on the upper core layer side of the upper pole layer. The presence of these taper portions causes a smooth magnetic flux flow between the upper core layer and the upper pole layer, thereby decreasing a leakage magnetic field from the joint between the upper core layer and the upper pole layer.
Since the upper surface of the lower core layer is polished to a flat surface having surface roughness Ra in the range of 0.0005 to 0.01 xcexcm, the trench can be precisely formed, and the magnetic recording track width can be further decreased.
Since the trench width is 1 xcexcm or less, more preferably 0.5 xcexcm or less, the magnetic recording track width can be set to 1 xcexcm or less.
In the thin film magnetic head of the present invention, the inclination angle of the apex surface of the back insulating layer is preferably in the range of 10 to 80 degrees with respect to the lower core layer.
With the apex surface having an inclination angle of less than 10 degrees, reactance between the upper and lower core layers is decreased to increase a leakage magnetic field from the upper core layer to the upper pole layer in the vicinity of the apex surface at the back end of the gap, thereby undesirably deteriorating recording efficiency. With the apex surface having an inclination angle of over 80 degrees, the sectional shape of the upper core layer cannot be inevitably formed to a smooth shape, and thus the sectional shape of the upper core layer becomes partially acute, thereby increasing a demagnetizing field in the upper core layer near the acute portion and undesirably deteriorating recording efficiency.
In the thin film magnetic head of the present invention, the insulating layer, the lower pole layer, the gap layer and the upper pole layer are preferably exposed from the medium-facing surface. In this construction, the magnetic recording track width in the medium-facing surface coincides with the trench width of the insulating layer, and thus the magnetic recording track width can be set to a small value. In addition, since the magnetic gap is exposed from the medium-facing surface, magnetic recording on the magnetic recording medium can be efficiently performed by a leakage magnetic field from the magnetic gap.
In the thin film magnetic head of the present invention, since the back insulating layer is made of a novolak resin, the apex surface can be formed in the back insulating layer by post baking, as described below. In addition, the upper pole layer can be formed by electroplating using the gap layer as an electrode, as described below, to improve the position setting precision of the gap depth, and the coil can be formed on the back insulating layer.
The insulating layer is preferably made of any one of AlO, Al2O3, SiO, SiO2, Ta2O5, TiO, AlN, AlSiN, TiN, SiN, Si3N4, NiO, WO, WO3, BN, and CrN, and it may comprise a single layer film or multilayer films. With the insulating layer comprising the above material, the trench can be formed by anisotropic etching without side etching, thereby improving the dimensional precision of the trench width to the trench depth.
The gap layer is preferably made of at least one of Au, Pt, Rh, Pd, Ru, Cr, NiMo alloys, NiW alloys, NiP alloys and NiPd alloys, and may comprise a single layer film or multilayer films. These materials are nonmagnetic materials which are not magnetized, and are optimum for forming the gap layer of the thin film magnetic head. These materials are also metallic materials, and can thus be laminated in the trench by electroplating using the lower core layer as an electrode.
The lower pole layer is preferably made of any one of FeNi alloys, FeNi alloys containing Fe at a higher concentration than Ni, and CoFeNi alloys, and may comprise a single layer film or multilayer films. These materials are magnetic materials having excellent soft magnetic properties, and are optimum for forming the core of the thin film magnetic head. These materials are also metallic materials and can thus be laminated in the trench by electroplating using the lower core layer as an electrode.
The upper pole layer is preferably made of any one of FeNi alloys, FeNi alloys containing Fe at a higher concentration than Ni, and CoFeNi alloys, and may comprise a single layer film or multilayer films. These materials are magnetic materials having excellent soft magnetic properties, and are optimum for forming the core of the thin film magnetic head. These materials are also metallic materials and can thus be laminated in the trench by electroplating using the gap layer as an electrode. Therefore, the lamination position of the upper pole layer can be set by the back insulating layer to improve the precision of gap depth position setting, and the upper pole layer can be securely formed so that the width of the upper pole layer coincides with the trench width.
The present invention also provides a method of producing a thin film magnetic head comprising upper and lower core layers which are extended from a back region to a pole tip region so that the end surfaces thereof are exposed from a medium-facing surface, and which are connected to each other in the back region; a coil provided around the connection portion between the upper and lower core layers; and a gap layer provided between the upper and lower core layers in the pole tip region. The method comprises laminating an insulating layer on the lower core layer; providing a trench in the insulating layer to extend it to the outside of the medium-facing surface in the pole tip region and extend from the pole tip region to the back region so that the bottom of the trench reaches the lower core layer; laminating a lower pole layer and the gap layer in the trench to connect the lower core layer and the lower pole layer to each other; forming a back insulating layer on the back region side of the gap layer to define the gap depth position of an upper pole layer; forming the upper pole layer on the pole tip region side of the gap layer so that the upper pole layer has the gap depth defined by the back insulating layer in substantially parallel with the medium-facing surface; forming a coil in the back region; and forming the upper core layer to join it to the upper pole layer in the pole tip region and partially cover the coil in the back region.
The back insulating layer of the present invention preferably comprises an apex surface which is formed in the vicinity of the gap depth by post baking to be inclined so that the thickness increases from the medium-facing surface side to the back region side.
The technique of forming the back insulating layer by using positive a photoresist comprising a novolak resin is selected.
The technique of forming the lower pole layer and the gap layer by electroplating using the lower core layer as an electrode is selected.
The technique of forming the upper pole layer by electroplating using the gap layer as an electrode is selected.
The trench width in the medium-facing surface is preferably set to 1 xcexcm or less.
In the present invention, the insulating layer is laminated on the lower core layer, and the trench is formed in the insulating layer to extend to the outside of the medium-facing surface in the pole tip region and extent from the pole tip region to the back region so that the bottom of the trench reaches the lower core layer, and the lower pole layer, the gap layer and the upper pole layer are formed in the trench, thereby permitting precise setting of the magnetic recording track width. Furthermore, since the back insulating layer comprising a novolak resin or the like is laminated on the back region side of the gap layer, and the upper pole layer comprises a metal or the like which permits electroplating, thereby permitting lamination of the upper pole layer by electroplating using the gap layer as an electrode. The back insulating layer is formed in the back region side of the gap layer to define the gap depth position of the upper pole layer, and thus the upper pole layer having the gap depth defined by the back insulating layer in substantially parallel with the medium-facing surface can be formed on the pole tip region side of the gap layer. There is thus no need to use liftoff resist, and the gap depth position can thus be recognized as viewed in plane, improving the setting precision of the gap depth position. There is also no need to use long throw sputtering having a low lamination rate, thereby improving productivity.
For example, the apex surface is formed in the back insulating layer comprising a novolak resin by post baking. In this case, the gap between the lower and upper core layers in the back region of the trench can be increased without formation of another insulating layer on the back insulating layer, thereby decreasing an internal leakage magnetic field and improving the performance of the magnetic head.
With the lower core layer planarized by polishing, the insulating layer laminated in the subsequent step is planarized, and thus the trench can precisely be formed by anisotropic etching, thereby permitting the magnetic recording track width to be set to a small value.
Furthermore, anisotropic etching for forming the trench permits improvement in the dimensional precision of the trench width to the trench depth without causing side etching.
In forming the trench, preferably, a mask layer is laminated on the insulating layer, and patterned so that portions of the insulating layer, which are exposed from the pattern, are anisotropically etched. The anisotropic etching is most preferably performed by a reactive ion etching method from the viewpoint that the trench can be formed with high dimensional precision.